math question

11 Plus Maths – Preparation and Information

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kaya
Posts: 11
Joined: Wed Dec 09, 2009 1:59 pm

math question

Post by kaya »

What is the difference of sum of the even numbers & sums of odd numbers between 1 - 1000.
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WP
Posts: 1331
Joined: Thu Jan 03, 2008 9:26 am
Location: Watford, Herts

Post by WP »

Pair them up:

(2-1) + (4-3) + (6-5) + ... + (1000-999)

There are 500 subtractions, each of which comes out as 1, so they add up to 500.
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kaya
Posts: 11
Joined: Wed Dec 09, 2009 1:59 pm

Post by kaya »

Thank you!! It was right!!! :D
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